1. Field of the Invention
The present invention relates to an improved process for manufacturing chlorocyanuric acids (including chloroisocyanuric acids), particularly trichloroisocyanuric acid and dichloroisocyanuric acid. More specifically, this invention pertains to a method for preparing chlorocyanuric acids having increased particle size.
2. Description of the Prior Art
The preparation of chlorocyanuric acids such as trichlorocyanuric acid or dichlorocyanuric acid is well known in the prior art.
One method for producing chlorocyanuric acid is described in U.S. Pat. No. 2,969,360 issued Jan. 24, 1961. In this process, cyanuric acid is fed along with aqueous alkali (in molar ratio corresponding to the number of chlorine atoms to be attached) and chlorine to an aqueous reaction zone which is maintained at a pH no higher than 9. The feed ingredients are added in essentially stoichiometric proportions. The crude chlorocyanuric acid precipitates from the solution as a solid slurry. The slurry product is periodically filtered to separate the crystalline products from the mother liquor whereupon the crystalline product is dried.
Prior art processes for producing chlorocyanuric acid have been beset with numerous difficulties most of which are attributable to deficient particle size. For example, considerable manufacturing downtime and rate variances have been experienced in the manufacture of trichlorocyanuric acid due to difficulties in dewatering which result in a slushy feed to the dryer. When very wet or slushy product material reaches the dryer it becomes necessary to reduce the production rate or shut down the unit in order to avoid packaging wet trichlorocyanuric acid. The primary cause for this problem is believed to be the very fine particle size produced in the process.
The patent literature reports other problems attributable to small particle size such as those relating to product separation (filtration), washing and drying as well as those relating to handling of the final dusty product. Small particle size is also said to decrease product stability.
It has been proposed heretofore in U.S. Pat. No. 3,120,522 issued Feb. 4, 1964, that chlorocyanuric acid crystals having increased size can be produced by adding to the reaction mixture from which these crystals are formed, from 50 to 1,000 ppm of a chlorinated hydrocarbon containing 1 to 6 carbon atoms and having not more than one hydrogen atom in its molecule.
It has further been proposed heretofore in U.S. Pat. No. 3,427,314 issued Feb. 11, 1969, that increased particle size can be achieved by heating trichlorocyanuric acid to from 130.degree. to 225.degree.C. with agitation and thereby causing the particles to agglomerate.
In addition, it has been proposed heretofore in U.S. Pat. No. 3,453,274 issued July 1, 1969, that crystal size of chlorocyanuric acids may be increased by adding from 50 ppm to 150 ppm of an alkali metal hydrocarbon sulfonate to the reaction mixture while maintaining the reaction mixture at a pH between 1.0 and 4.5.
The principal object of the present invention is to provide a superior chlorocyanuric acid product of increased particle size which overcomes many of the deficiencies experienced in the prior art, particularly the dewatering and drying problems. This object has been accomplished through use of certain promoters during the manufacturing process.